Write character to cursor seems to break program counter

[clubby789]

When I set ah to 0x0a, then call int 10h, the program counter seems to jump to uninitialized memory: 0x7c28 to 0xd2a0. If I use 0x0e (TTY mode) the character prints fine.

PutChar:
    mov ah, 0xa
    int 0x10
    leave
    ret
[ ... ]
mov al, 'H'
call PutChar